Field of the Invention
The present invention relates to a power supply apparatus and an image forming apparatus.
Description of the Related Art
A switched-mode power supply converts AC voltage of a power supply such as a commercial power supply to DC voltage. Methods, for example a method of Japanese Patent No. 05645979, have been proposed for reducing noise in terminal voltage, which is conductive interference for a power supply port of a switched-mode power supply. Japanese Patent No. 05645979 proposes a switching frequency fluctuation control method of a switched-mode power supply.
When switching frequency fluctuation control is performed, however, a transformer used in the switched-mode power supply produces sound due to periods of varying the switching frequency. Another problem is the increase of terminal noise caused by the switched-mode power supply.